The present invention generally relates to field-effect transistor (FET) gate stacks containing different silicon material layers having different hydrogen content, and methods of making these gate stacks.
The metal oxide semiconductor field-effect transistor (MOSFET) is a transistor used for amplifying or switching electronic signals. The MOSFET has a source, a drain, and a metal oxide gate electrode. The metal gate is electrically insulated from the main semiconductor n-channel or p-channel by a thin layer of insulating material, for example, silicon dioxide or hafnium oxide, which makes the input resistance of the MOSFET relatively high. The gate voltage controls whether the path from drain to source is an open circuit (“off”) or a resistive path (“on”).
The threshold voltage (Vt) of a FET is the minimum gate-to-source voltage differential needed to create a conducting path between the source and drain. Vt control is an important feature in FET-based technology. The ability to achieve multiple Vt with a given gate stack, thereby limiting integration complexity, is an ongoing challenge in the industry. Multi-Vt devices allow the coupling of hybrid systems designed for high-performance and low power consumption. Prior methods of achieving multiple Vt involves using different dielectric capping materials or metal electrode tuning.
There remains a need in the art for solutions to achieve multiple Vt with a given gate stack, particularly with high mobility channels such, as InGaAs.